arrayout_demo.va

`include "disciplines.vams"

// Enhancement-20 demonstration: array OUTPUT and INOUT arguments to analog
// functions (completing Enhancement-18's input-only array arguments).
//
//   * `make_taps` writes a geometric tap array via an OUTPUT array argument.
//   * `normalize` scales an array in place via an INOUT array argument.
//
// The gain is the sum of the normalized taps, which is 1 by construction for any
// `ratio`, so V(out) tracks V(in) exactly -- but only if both the output write
// (filling the taps) and the inout write (normalizing them) actually reach the
// caller's array. A broken writeback leaves the taps zero/unnormalized and the
// gain wrong.
module arrayout_demo(in, out);
    input in;
    output out;
    electrical in, out;

    parameter real ratio = 0.5 from (0:inf);

    // OUTPUT array argument: fill w with 1, ratio, ratio^2, ratio^3
    analog function real make_taps;
        input r;    output w;
        real r;     real w[0:3];
        integer i;
        begin
            w[0] = 1.0;
            for (i = 1; i < 4; i = i + 1) w[i] = w[i - 1] * r;
            make_taps = 0.0;
        end
    endfunction

    // INOUT array argument: normalize in place so the elements sum to 1
    analog function real normalize;
        inout w;    real w[0:3];
        integer i;  real s;
        begin
            s = 0.0;
            for (i = 0; i < 4; i = i + 1) s = s + w[i];
            for (i = 0; i < 4; i = i + 1) w[i] = w[i] / s;
            normalize = s;
        end
    endfunction

    real taps[0:3];
    real g;
    real dummy;
    integer i;

    analog begin
        dummy = make_taps(ratio, taps);   // fill taps (output arg)
        dummy = normalize(taps);          // normalize in place (inout arg)
        g = 0.0;
        for (i = 0; i < 4; i = i + 1) g = g + taps[i];   // = 1.0 for any ratio
        V(out) <+ g * V(in);
    end
endmodule